Caption: Scanning electron micrograph of open stomata on the surface of a tobacco leaf Nicotiana tabacum. Stomata are breathing pores scattered over the leaf surface, & sometimes stem, that regulate the exchange of gases between the leaf's interior & the atmosphere. Stomatal closure is a natural response to darkness or drought as a means of conserving water. Each pore is controlled by the turgor of two guard cells (sides seen beneath pore's opening) on either side of it; when they are full of water the pore is open; when they lose turgor, the pore closes. Some of the pores are still growing (pimple in front, unopened in back). Magnification X1100 (at 10x8 size).